1. Field of the Invention
The present invention relates to an image forming device using a thermal head. More specifically, the present invention relates to a method and apparatus for adjusting the alignment of a thermal head of an image forming device.
2. Description of Related Art
A thermal printing device typically refers to an image forming device for applying heat to an ink ribbon contacting a medium to move the ink to the medium, or for applying heat from a thermal head to a medium, where an ink layer reacting with the heat develops a predetermined color.
FIG. 1 is a cross sectional view of a typical thermal recording medium. The medium includes a base sheet 11 and ink layers provided on both sides of the base sheet 11, that is, first and second surfaces 10a and 10b, in predetermined colors. The ink layers are provided in different colors. For example, yellow (Y) and magenta (M) layers can be sequentially provided on the first surface 10a, and a cyan (C) layer can be provided on the second surface 10b. The base sheet 11 is preferably comprised of a transparent material. A reflective layer 13 is provided and reflects light from the first surface 10a to display color images.
FIG. 2 is a perspective view showing a typical arrangement of an image forming device using a thermal head. The image forming device of FIG. 2 comprises a thermal head 100, a thermal head nozzle 110, a platen roller 120, and a moving unit 130. The moving unit 130 comprises a motor 140, a driving roller 150, a driven roller 160, and a medium sensor 170.
The thermal head 100 applies heat to a medium moved by the moving unit 130. The thermal head nozzle 110 provides ink required in printing to the platen roller 120. Here, the medium is interposed between the thermal head 100 and the platen roller 120. The platen roller 120 supports the medium to adsorb the ink, and rotates according to the movement of the medium.
The motor 140 is comprised of a driving source for supplying a target medium to the thermal head 100. The driving roller 150 rotates while engaged with the motor 140 to move the medium. The driven roller 160 also rotates while engaged with the driving roller 150 to assist in moving the medium. Here, the medium is interposed between the driving roller 150 and the driven roller 160. The media sensor 170 is provided to detect a position of the target medium.
However, when the heat is applied to the thermal recording medium shown in FIG. 1, by using two thermal heads to make a color print on the medium as shown in FIG. 3, a screen may not be printed in designed colors due to a distance difference between the two thermal heads and a difference of the moving path of the medium. In this case, there is a need to adjust the alignment to match the printing positions of the two thermal heads.
Accordingly, a need exists for a system and method for adjusting the alignment of multiple thermal heads, and for moving data to compensate for the printing positions of the thermal heads.